1. Field of the Invention
The present invention relates to an image correction processing apparatus and method for performing hand-movement correction at the time of shooting an image.
2. Description of the Related Art
Shooting apparatus such as video cameras, digital still cameras, and the like have undergone a reduction in size and weight for ease of portability. It has consequently become difficult to avoid hand movement or camera shake at the time of shooting a picture. In addition, since the recent models are equipped with zoom lenses of high power, hand movement can be easily noticeable when performing telescopic shooting. Furthermore, due to the high quality of the shot image, when the image is output on a display or a printer with high resolution, the blur and distortion of the image caused by the motion often become evident.
One of methods for correcting hand movement is a real-time feedback control method where angular velocity caused by hand movement is detected by using a gyro sensor for detecting hand movement and is immediately fed back into the shooting system of a camera so as to avoid image blurring due to hand movement. Another method includes steps for detecting a motion vector caused by hand movement in a shot image and performing image processing for eliminating the effects caused by hand movement.
Japanese patent application publication number 2007-221631 discloses a method for correcting image distortion caused by hand movement. According to the method, when it is determined that an optical zooming operation is performed, the difference between a motion vector detected in the motion vector detecting step and a optical zoom vector calculated in the optical zoom component calculating step is computed. The hand-movement vector of the shot image is then computed from the resultant motion vector obtained from the difference calculation.
Japanese patent application publication number 2008-160274 discloses the following method. In comparing a reference image and an image for comparison and calculating the motion vector required for hand-movement correction, if the optical zoom factor has been changed, the method performs a correction on the magnification ratio of the reference image and the image for comparison so that the two images are of the identical optical zoom factor.
Japanese patent application publication number H7-264464 discloses an apparatus for detecting blurring of an image by detecting a motion vector for every divided area of the screen. If an optical zooming operation is detected, the apparatus switches control from using the motion vector detected for every divided area to using only the motion vector detected for the divided area at the central position of the screen.
According to the method disclosed in Japanese patent application publication number 2007-221631, the components of the changes in the image are calculated based on the position and/or velocity of the optical zooming. For the velocity of the optical zooming, about ten levels of the velocity would need to be considered for the calculation. A problem of the method is that it requires a large-sized table containing the position and velocity of the optical zooming and also requires a large amount of computation of the optical zooming components in the motion vector detecting step.
According to the method disclosed in Japanese patent application publication number 2008-160274, the camera needs to be provided with a reverse-zooming circuit for performing correction on the magnification ratio of the reference image and the image for comparison in order to adjust the zoom factor of the two images to be identical, resulting in additional cost.
The method disclosed in Japanese patent application publication number H7-264464 practically lacks in reliability for the following reason. Although there is no effect caused by the optical zooming at the central position of the screen, if the luminance level of the divided area at the central position of the screen is uniform, the detection of the motion vector becomes impossible.
Due to the above-mentioned problems, according to conventional hand-movement correction based on the motion vector detection, it is common that the correction process is temporarily terminated during the optical zooming operation, and simply the shot image is extracted from the center and output without performing any hand-movement correction.